1. Field of the Invention
This invention relates to a process for removing hydrogen sulfide from sour gas streams, and more particularly, but not by way of limitation, to a process for removing hydrogen sulfide from a sour gas stream to provide a sweet gas stream and an aqueous solution of sodium hydrosulfide.
2. Brief Description of the Prior Art
Processes have been known for producing sweet gas streams from sour gas streams and for producing aqueous solutions of sodium hydrosulfide from such sour gas streams. Typical of such processes is the process disclosed in U.S. Pat. No. 3,839,548 issued to Jackson. This patent discloses a process for producing sodium hydrosulfide solutions substantially free of sodium carbonate from a refinery sour gas stream by contacting the refinery sour gas stream with a fresh aqueous sodium hydroxide solution in continuous cocurrent interfacial two-phase flow, such as a thin film contact apparatus, separating the gas phase into a sweet gas substantially free of hydrogen sulfide, and recovering the aqueous phase as a sodium carbonate free solution of sodium hydrosulfide.
Another process for removing hydrogen sulfide from a refinery gas stream to provide sodium hydrosulfide solutions of high concentration is disclosed in Canadian Pat. No. 520,874 issued to Maschwitz. This patent discloses a process for manufacturing sodium hydrosulfide solutions from a refinery sour gas stream containing hydrogen sulfide wherein the refinery sour gas stream is contacted with an aqueous sodium hydroxide solution containing not less than about 25% by weight of solutes consisting essentially of sodium hydrosulfide and sodium sulfide. A portion of the absorbent withdrawn from the absorber and containing not less than 25% by weight of sodium hydrosulfide is mixed with fresh aqueous sodium hydroxide solution and recycled as fresh absorbent to the absorber for contact with additional amounts of the refinery sour gas stream. The amount of sodium hydrosulfide employed for mixing with the fresh sodium hydroxide solution is an amount sufficient to prevent precipitation of the sodium sulfide at the operating conditions of the absorber.